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    <h1>SC3030 – ShellCheck Wiki</h1>
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    <h2 id="in-posix-sh-arrays-are-undefined">In POSIX sh, arrays are
undefined.</h2>
<h3 id="problematic-code">Problematic code:</h3>
<div class="sourceCode" id="cb1"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb1-1"><a href="SC3030.html#cb1-1" aria-hidden="true" tabindex="-1"></a><span class="co">#!/bin/sh</span></span>
<span id="cb1-2"><a href="SC3030.html#cb1-2" aria-hidden="true" tabindex="-1"></a><span class="va">x</span><span class="op">=</span><span class="va">(</span> foo bar <span class="st">&quot;Hello World&quot;</span> <span class="va">)</span></span>
<span id="cb1-3"><a href="SC3030.html#cb1-3" aria-hidden="true" tabindex="-1"></a><span class="cf">for</span> word <span class="kw">in</span> <span class="st">&quot;</span><span class="va">${x</span><span class="op">[@]</span><span class="va">}</span><span class="st">&quot;</span></span>
<span id="cb1-4"><a href="SC3030.html#cb1-4" aria-hidden="true" tabindex="-1"></a><span class="cf">do</span></span>
<span id="cb1-5"><a href="SC3030.html#cb1-5" aria-hidden="true" tabindex="-1"></a>  <span class="fu">touch</span> <span class="st">&quot;</span><span class="va">$word</span><span class="st">.dat&quot;</span></span>
<span id="cb1-6"><a href="SC3030.html#cb1-6" aria-hidden="true" tabindex="-1"></a><span class="cf">done</span></span></code></pre></div>
<h3 id="correct-code">Correct code:</h3>
<p>Consider switching to a shell that does support arrays, such as
<code>bash</code> or <code>ksh</code>, by changing the shebang.</p>
<p>Alternatively, if you only need a single array at a time, you may be
able to rewrite to use the positional parameters:</p>
<div class="sourceCode" id="cb2"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb2-1"><a href="SC3030.html#cb2-1" aria-hidden="true" tabindex="-1"></a><span class="bu">set</span> <span class="at">--</span> foo bar <span class="st">&quot;Hello World&quot;</span></span>
<span id="cb2-2"><a href="SC3030.html#cb2-2" aria-hidden="true" tabindex="-1"></a><span class="cf">for</span> word <span class="kw">in</span> <span class="st">&quot;</span><span class="va">$@</span><span class="st">&quot;</span></span>
<span id="cb2-3"><a href="SC3030.html#cb2-3" aria-hidden="true" tabindex="-1"></a><span class="cf">do</span></span>
<span id="cb2-4"><a href="SC3030.html#cb2-4" aria-hidden="true" tabindex="-1"></a>  <span class="fu">touch</span> <span class="st">&quot;</span><span class="va">$word</span><span class="st">.dat&quot;</span></span>
<span id="cb2-5"><a href="SC3030.html#cb2-5" aria-hidden="true" tabindex="-1"></a><span class="cf">done</span></span></code></pre></div>
<p>or strings with carefully chosen delimiters:</p>
<div class="sourceCode" id="cb3"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb3-1"><a href="SC3030.html#cb3-1" aria-hidden="true" tabindex="-1"></a><span class="va">x</span><span class="op">=</span><span class="st">&#39;foo</span></span>
<span id="cb3-2"><a href="SC3030.html#cb3-2" aria-hidden="true" tabindex="-1"></a><span class="st">bar</span></span>
<span id="cb3-3"><a href="SC3030.html#cb3-3" aria-hidden="true" tabindex="-1"></a><span class="st">Hello World</span></span>
<span id="cb3-4"><a href="SC3030.html#cb3-4" aria-hidden="true" tabindex="-1"></a><span class="st">&#39;</span></span>
<span id="cb3-5"><a href="SC3030.html#cb3-5" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb3-6"><a href="SC3030.html#cb3-6" aria-hidden="true" tabindex="-1"></a><span class="bu">printf</span> <span class="st">&#39;%s&#39;</span> <span class="st">&quot;</span><span class="va">$x</span><span class="st">&quot;</span> <span class="kw">|</span></span>
<span id="cb3-7"><a href="SC3030.html#cb3-7" aria-hidden="true" tabindex="-1"></a>  <span class="cf">while</span> <span class="va">IFS</span><span class="op">=</span><span class="st">&#39;&#39;</span> <span class="bu">read</span> <span class="at">-r</span> <span class="va">word</span></span>
<span id="cb3-8"><a href="SC3030.html#cb3-8" aria-hidden="true" tabindex="-1"></a>  <span class="cf">do</span></span>
<span id="cb3-9"><a href="SC3030.html#cb3-9" aria-hidden="true" tabindex="-1"></a>    <span class="fu">touch</span> <span class="st">&quot;</span><span class="va">$word</span><span class="st">.dat&quot;</span></span>
<span id="cb3-10"><a href="SC3030.html#cb3-10" aria-hidden="true" tabindex="-1"></a>  <span class="cf">done</span></span></code></pre></div>
<h3 id="rationale">Rationale:</h3>
<p>Arrays are specific to Bash and Ksh, but you are using them in a
script declared to run with <code>sh</code> or <code>dash</code>. These
shells do not support arrays at all. You should either switch to
Bash/Ksh, or rewrite the script to not use arrays.</p>
<p>There are no great replacements, especially not that can be
mechanically applied, but using the positional parameters or a delimited
string works in many cases, as shown in the examples.</p>
<h3 id="exceptions">Exceptions:</h3>
<p>None.</p>
<h3 id="related-resources">Related resources:</h3>
<ul>
<li>Help by adding links to BashFAQ, StackOverflow, man pages, POSIX,
etc!</li>
</ul>
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